Biomass is an abundant and renewable resource. As a result of such availability of biomass there is a significant need for improved methods of biomass conversion. There is a vast body of work of others skilled in the art attempting to convert biomass sources into desired, high-value compounds. See for example, U.S. Pat. No. 7,494,637. However, biomass conversion methods have consistently failed to yield high volumes and/or provide efficient methods to convert biomass sources into high-value compounds as has been achieved by the present invention. For example, current industrial production of compounds such as propylene glycol and ethylene glycol require the use of petroleum and do not convert renewable sources. In such methods, ethylene or propylene are epoxidized from alkenes to form oxides which are hydrolyzed to form the ethylene or propylene glycol. As a result, such methods require significant and undesirable dependence on petroleum for the products of these biomass conversion processes.
Methods to efficiently convert biomass sources into these same desired compounds, including propylene glycol and ethylene glycol, would minimize the necessity of petroleum products for the production of commercially useful low-molecular-weight compounds and chemicals. Biomass conversion would further limit the large amounts of cellulosic waste, or biomass, which if not utilized is generally left to decay, either in a landfill or in open fields. Therefore, there is significant demand for the use of renewable starting materials, such as biomass, to produce valuable products as described in the present invention.
Presently, very little biomass is converted into commercially-useful compounds. This is largely due to the fact that conversion of biomass, such as agricultural waste products, is difficult due to the complex structure of plant cell walls. The plant cell wall is made of lignocellulose, which consists approximately of cellulose (38-50%), hemicellulose (17-32%) and lignin (15-30%). These components are difficult to break down as the cellulose is made up of crystalline bundles of polysaccharide chains of β-1,4 bonded glucose molecules. Additionally, the hemicellulose consists of chains of amorphous combinations of the sugar molecules xylose, mannose and arabinose. The final component of lignocellulose is lignin, a macromolecule of substituted phenols acting to bind together the lignocellulose matrix which provides strength to cell walls.
Various methods for converting lignocellulose require the use of catalysts, enzymes, or other expensive ingredients to depolymerize and/or decrystallize the complex structure of the lignocellulose of biomass precluding the development of an efficient and effective one-step conversion process. See M. Jacoby, Chemicals from the Garden, C&EN 26-28 (2009). Strong acids are often used; however, the use of these requires the refining of the cellulosic materials to ensure sufficient contact between the acid and the biomass. See e.g., U.S. Pat. No. 5,562,777. Such methods further result in large amounts of waste products, incurring additional costs.
Therefore, it is an object of the present invention to develop methods of converting cellulose and related carbohydrate materials to commercially-useful low-molecular-weight compounds.
It is a further object of the present invention to develop methods to convert cellulose and related carbohydrate materials to ethylene glycol, propylene glycol, glycerin, methanol, hydroxyacetone, glycolaldehyde and dihydroxyacetone.
A still further object of the present invention is to develop a single step conversion method to produce the low-molecular-weight compounds without the need for hydrogen gas, strong acids, metal catalysts, or enzymes.